Transapical aortic valve implantation: never limited by aortic disease or vascular access, but always needed?

Shortly after the first transcatheter aortic valve implantation (TAVI) was performed by Alain Cribier in 2002 through a transseptal antegrade approach, percutaneous TAVI moved towards retrograde, transfemoral (TF) access, as this was technically less challenging. In parallel, transapical (TA) TAVI was introduced by Fred Mohr and Michael Mack in 2004. While TF-TAVI offered the potential of reduced trauma, it was always limited by vascular access, a particular issue during the early years when devices were still of large size. The antegrade TA route was instead not limited by vascular access and offered a very stable, direct approach to the aortic valve. However, the procedure can only be performed under general anaesthesia and the limited left-sided thoracotomy causes surgical trauma. Subsequently, and given that the first balloon-expandable transcatheter heart valve was available for TF and TA access, numerous TAVI trials (family of PARTNER Trials) were performed using both access routes. In these studies, patients with suitable vascular access underwent TF therapy, whereas the remaining benefitted from TA access. As a consequence, patients with severe aortic and peripheral vascular disease were frequently found in the TA cohorts, which also suffered from more comorbidities such as renal and coronary artery disease. As a result of the latest PARTNER Trials [1], where TF access was found to have the lowest periprocedural mortality, a TF-first approach to TAVI was supported. It is important to note, however, that there has never been a direct randomized trial between TF- and TA-TAVI. In fact, in one of the latest post-market release studies, the SOURCE 3 Registry, cardiovascular mortality was not different between TF and TA access routes [2]. Most recent European and North American guidelines support the TF-first approach. General anaesthesia can be avoided and newly developed small and steerable devices facilitate peripheral vascular access and atraumatic passage of the aorta. As a result, non-TF procedures are currently only performed in around 10–15% of all TAVI cases in large TAVI centres [1, 2]. With this in mind, the experience from Useini et al. [3] is very valuable to get an idea which role TA-TAVI has in the treatment of those patients seen unsuitable for TF access. The group has an excellent experience using TA technique, and over the last 10 years, they have performed more than 60% of their TAVI’s through this route—a much higher proportion than other TAVI centres [1, 2]. Around 40% of their patients in this study suffered from aortic disease with limited access, and in around 60% of those the aortic comorbidity potentially increased the risk of thrombotic embolization or aortic trauma. While TA-TAVI resulted in a low 30-day mortality of 6%, it sharply rose to 16% at 60 days. Interestingly, all of those patients who died between 30 and 60 days suffered from severe chronic obstructive pulmonary disease. Strokes were observed in 4% of patients at 30 days. The known causes of death were cardiac related in 29%, followed by pulmonary (19%), cerebral (10%) and multiorgan failure (10%). The high number of pulmonary complications and pre-existing respiratory disease raises the question if mortality would have been lower, if the additional trauma caused by the lateral thoracotomy would have been avoided? A number of groups have developed alternative non-TF-TAVI access routes for that very reason. Direct aortic access also requires surgical opening of the chest under general anaesthesia [4]. In contrast, using axillary/subclavian and carotid access, thoracotomy and general anaesthesia can be avoided [5, 6]. This offers access to the aortic valve without irritating the descending and ileo-abdominal aorta, which is particularly attractive in those patients with aortic and peripheral vascular disease. However, internal thoracic artery grafts post-coronary bypass surgery face traumatic risk during transaxillary TAVI. They are a limitation for the usual approach from the left side and in addition, not all transcatheter devices are equally suitable for this access route [5]. Carotid access is not limited by previous coronary surgery. However, the significant stroke rate and its consequences after TAVI in general, may have contributed to a certain hesitation of cardiologists and surgeons to implement this access route in larger numbers [6]. With respect to the observed stroke rate of 4% and its consequences in terms of mortality, the question remains about the authors’ approach in those patients who face high risk for periprocedural embolization. A number of TAVI groups use cerebral embolization protection devices to reduce this risk, but it still remains unclear what their role is during routine TAVI procedures. In addition, there is some controversy with regards to TAVI treatment of patients with porcelain aortas [7]. It can be noted that in the presented cohort, 36% of patients underwent a TA procedure due to this comorbidity, and in many TAVI centres, these patients undergo TF therapy nowadays [2, 7]. Most importunately, one must identify patients with intraluminal aortic calcifications, which would increase the embolic risk, during their pre-assessment. Nevertheless, from the previous work of the authors of this publication, there is evidence that TA access may be superior to the TF route in patients with porcelain aortas [8]. It is important to note that this study includes outcomes using historic, larger and less-steerable transcatheter devices, and therefore may be no longer representative in our current practice. From the presented evidence, it is obvious that the key for excellent TAVI outcomes is the availability of the full armamentarium of transcatheter heart valve options and TAVI techniques. Critical discussions of patients, involving the entire team of cardiologists, cardiovascular surgeons and anaesthetists are recommended to identify the optimal treatment approach for individual patients. In this respect, more recent non-TF access routes should also be considered to address potential shortfalls from TA-TAVI. Nowadays, while TAVI is offered to elderly patients who face low risk for surgery, it is also important to identify those patients with aortic stenosis, in whom aortic comorbidities can be treated in combination with surgical aortic valve replacement. In this setting, minimally invasive surgery offers also the option to replace aortic root, ascending aorta and even aortic arch disease at the same time.